This invention relates to prediction of biological properties. More particularly, the present invention is directed to the measurement of multiple membrane affinities of test compounds, methods and compositions useful for acquiring data characteristic of such affinities, and a method and system for using such data alone or in combination with other molecular descriptors for the prediction of biological activity.
There has been much research and development effort directed to the definition of screening methods capable of identifying drug leads. The goal of such efforts is to define efficient methodologies for predicting biological activity in vivo by using empirically definable (or calculatable) descriptors to predict biological activity without the time investment and expense in costly animal studies. For many years most drug screening methods were based on conventional biological activity assays. More recently assays have been developed that predict cell membrane transport properties of test compounds. Generally drug leads are generated by comparing biological and physical properties of test compounds with known compounds having recognized biological activity in vivo. There is a significant body of literature directed to prediction of biological activities based on comparison of physical, chemical and biological descriptors and the use of pattern recognition analysis of such descriptors as part of drug screening protocols.
The present invention is directed to a method of screening test compounds for probable biological properties based principally on correlation of numerical values characteristic of their interaction with two or more membrane mimetic surfaces with corresponding values for control compounds of known biological activities/function. The method is grounded on the premise that compounds with similar sets of membrane binding properties will have similar pharmacological properties and/or biological activities. The membrane binding properties of test compounds can be calculated, or they can be determined empirically with use of, for example, liposomes, immobilized artificial membranes, such as those described in U.S. Pat. No. 4,931,498, the disclosure of which is incorporated herein by reference, Langmuir-Blodgett films, computer chips or similar devices with immobilized lipids, capillary zone elcctrophoresis columns coated with membrane lipids, and the like.
In one embodiment of this invention vector calculus is utilized to pattern match membrane interaction values of test compounds with control compounds to predict biological properties. The pattern matching protocol can be applied to data sets containing only values characteristic of multiple membrane interactions, or such data sets can include other biologically significant molecular descriptors such as molecular surface area, molecular weight, dipole moment, octanol-water partition coefficients, molecular volume, membrane diffusion coefficients, metabolism rates, cell efflux rates, etc.
In another embodiment, membrane binding data are obtained for test compounds and control compounds for use in accordance with this invention using immobilized artificial membrane chromatographic substrates in high pressure liquid chromatographic systems using aqueous mobile phases. Data relevant to the thermodynamics and kinetics of compound/membrane interaction is reflected in retention time and peak width, respectively. All data are preferably normalized relative to a standard compound or a set of compounds, for example, a set of compounds having a common biological activity or function.
This invention also provides novel carboxyl-functional, head group-protected phospholipids useful for preparing immobilized artificial membrane structures useful for acquiring membrane interaction data. They are prepared by novel high yielding transphosphitidylation of phosphatidylcholine derivatives using phospholipase D in the presence of protected alcohols.